One of the factors contributing to the overwhelming popularity of Facebook is that third parties are allowed to create applications for the site. Here are some of the features that have made Facebook a force to contend with:

Halloween Picture Alert: Tells you to change your profile picture after your Halloween one has been left on there for too long

Shove: Members can "shove," with varying degrees of intensity, other members who are really starting to annoy them

Carbon Offset Offsetter: With every click, a 6-year-old child in India is forced to dig up 50 pounds of coal and set it on fire

MySpace Layouts and Skins: Make your Facebook page look so much like MySpace that you'll wonder why you joined yet another social network

Thick as a Brickster: Plays the entirety of Jethro Tull's Thick As A Brick album

Ad space: Allows you to check out really awesome advertisements from the coolest companies, free of charge

Jesus Christ, I Wish You Would Fucking Die LOL!: Lighthearted way to inform your coworkers and dull college classmates that you do not wish to play Scrabulous with them